How did THAT get into my lawn: Onion Grass

Onion Grass or Wild Onion thrives in heavy soils and tolerates cool temperatures and even drought. However, with proper consistent techniques, this weed can be controlled and eventually eliminated.

Managing Wild Onion

Onion Grass or Wild Onion is a common lawn weed that looks similar to the chive plant.

A little about Onion Grass – Onion Grass is a perennial weed meaning that it can and will live for several years rather than die off each season. They survive winter months by storing food in their roots and bulbs then sprout new plant material each season. Wild onion is the cousin to the garden variety that you use in your kitchen and grows in patches. Its leaves, being the part that you see, look similar to green onion that is sold in store and have an onion-like odor when crushed or torn.

How did THAT get into my lawn? – Wild Onion can be a tough weed to control. Once these weeds have established themselves in your lawn, they spread rapidly and will take a few seasons of care to eradicate. This weed works in the lawn a few ways to establish itself; the visible plant will produce a flower and drop seeds to establish a thicker patch while the bulbs underground will become new plants. Wild Onion is a cool weather weed, showing up in lawns mainly during late fall and early spring, as the weather warms the bulbs will go dormant until the temperature lowers.

What can I do? – As always, the best defense against any weed is a thick, well maintained lawn. When the lawn is thin, it allows weeds to push past the grass’ root system and flourish in the lawn. Aeration and seeding will help to thicken an established lawn but if the area is too thin, a full seeding may be required. By aerating, the lawn will receive extra nutrients to enter the soil during fertilization treatments and give your grass the ability to strengthen its root system and keep weeds from germinating. For wild onion, it is best to attack from as many angles as possible to prevent these weeds from continuing to spread.

Regular mowing will keep the visible leaves from flowering, slowing its ability to produce seeds. Remember to keep your lawn at 3.5”, the shorter your grass, the weaker the root system under the soil line!

Attempting to pull these weeds is NOT encouraged. If the blades of the plant snap or the tiniest bit of root system or bulb is left, the plant will grow right back and spreads quickly.

Post-emergent herbicide. Using a selective herbicide that will not kill your existing grass is a good choice to kill off the whole plant including its bulbs and root system. Once the weed is completely dead, aeration and seeding will help to fill in the small patches left behind. Regular applications of this type of control will be necessary to eliminate existing plants due to their underground bulb system and waxy leaves.

These plants are remarkably vigorous, tolerant, and fast growing — too bad they also are unwanted. Learn the weeds most familiar to lawns in this area, the conditions that sustain them, and techniques to control them.